1. Field of the Invention
The present invention relates to an apparatus and method for spreading and de-spreading data using a pair of child orthogonal variable spreading factor (OVSF) codes; and, more particularly, to an apparatus and method for spreading and de-spreading data selectively using a single orthogonal variable spreading factor (OVSF) code or a pair of child OVSF codes according to a channel condition in CDMA or WCDMA communication scheme including a RAKE structure that uses multi-path diversity to improve a signal to noise ratio in order to reduce inter-symbol interference (ISI) induced by mobility.
2. Description of Related Art
When a mobile station having mobile communication equipment communicates with a base station, the mobile station performs a fast power control operation in a slot unit or uses multipath diversity to improve a signal to noise ration (SNR), thereby improving the processing capacity of an overall system.
Since the channel state dynamically varies due to the mobility of the mobile station, the channel estimation error and inter-symbol interference (ISI) are induced. Although the power control operation is performed in a slot unit, it cannot correct the channel estimation error and ISI.
Hereinafter, a conventional apparatus for spreading and de-spreading data using a single code will be described with reference to FIGS. 1 and 2.
FIG. 1 is a block diagram illustrating a conventional spreading apparatus, and FIG. 2 is a block diagram illustrating a conventional de-spreading apparatus.
As shown in FIG. 1, the conventional spreading apparatus spread data using an orthogonal variable spreading factor (OVSF) single code allocated from a network.
For example, when the conventional spreading apparatus spreads four data bits of {b0, b1, b2, b3} from I-channel, the conventional spreading apparatus generates an OVSF cod C2n+1,0 using the allocated spreading factor (SF) index, and sequentially spreads the four data bits like as C2n+1,0*b0, C2n+1,0*b1, C2n+1,0*b2, and C2n+1,0*b3.
Then, the conventional de-spreading apparatus using a single code, as shown in FIG. 2, generates an OVSF code C2n+1,0 using a SF index allocated identically to that of the conventional spreading apparatus and extracts original four data bits from the de-spread signal.
The conventional spreading and de-spreading apparatus using the single code can significantly remove the channel estimation error and the ISI, which are induced by channel state that dynamically varies due to the mobility of the mobile station. The conventional spreading and de-spreading apparatus, however, requires a large amount of complex computation.